Micro- and Nano-Mechanics of Active Biopolymer Networks

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The research objective of this award is to develop new analytic and numerical approaches to examine the complex relationship of filament mechanics and network structure to the collective elastic properties of semiflexible networks. Semiflexible networks are cross-linked aggregates of stiff polymers. They are fundamentally different from the better understood polymeric materials that are the usual products of modern synthetic chemistry. Under applied stress semiflexible networks can store elastic energy in both the stretching and bending of the constituent filaments, while traditional polymer networks, which are composed of highly flexible polymer chains, store elastic energy only in filament stretching. The most common example of a semiflexible network is found in the cytoskeleton of living cells. There stiff protein filaments (F-actin) are cross-linked to form a stress-bearing framework that gives the cell its mechanical rigidity. Recent experiments have shown that small changes in network architecture and in the action of molecular motors can lead to significant changes the elasticity of these F-actin networks. This research will explore in detail how these changes in network structure and non-equilibrium steady-state (via the action of the molecular motors) leads to large mechanical changes of the network. Among the benefits of the successful completion of this work will be a deeper understanding of the design principles for building a new class of light-weight, mechanically tunable materials. The theory will also address new biomimetic approaches to materials design that use the action of endogenous motors to tune mechanical properties through the modification of the materials non-equilibrium steady-state. Such research will enable the creation of new bio-compatible materials whose mechanical properties can be precisely controlled. These materials may find applications in the promotion of wound healing. Finally, this research will assist the training of students/postdocs working at the interface of the physics, biology, and engineering.